Mechanochemical synthesis and structural characterization of the I₂-II-IV-VI₄ quaternary chalcogenide Ag₂CdGeSe₄

Ag 2 CdGeSe 4 – a I 2 -II-IV-VI 4 quaternary chalcogenide – was synthesized by a mechanochemical synthesis route with a subsequent annealing step inside of a glass ampoule. Detailed analysis and structural investigation using X-ray powder diffraction (PXRD) indicate that Ag 2 CdGeSe 4 crystallizes in the wurtzstannite-type structure with space group Pmn 2 1 . For Rietveld refinements, all cubic diamond/sphalerite- and hexagonal diamond/wurtzite-related structure types including all subgroups of the wurtzstannite-type structure were considered. Quantum-chemical calculations were carried out at density-functional theory (DFT) level. The results do not allow an unambiguous verification of the experimentally observed Ag 2 CdGeSe 4 type, due to the small energy differences between the structures. Comparison of calculated and measured UV/Vis data, however, support the results of the Rietveld refinement.